CN217768423U - Negative electrode plate, secondary battery, battery module, battery pack and electric device - Google Patents
Negative electrode plate, secondary battery, battery module, battery pack and electric device Download PDFInfo
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- CN217768423U CN217768423U CN202220272014.9U CN202220272014U CN217768423U CN 217768423 U CN217768423 U CN 217768423U CN 202220272014 U CN202220272014 U CN 202220272014U CN 217768423 U CN217768423 U CN 217768423U
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Abstract
The application provides a negative pole piece, a secondary battery, a battery module, a battery pack and an electric device. The negative pole piece comprises a negative pole current collector and a negative pole film layer arranged on at least one surface of the negative pole current collector; the negative electrode film layer comprises carbon material sections and silicon/carbon composite material sections, and the carbon material sections and the silicon/carbon composite material sections are alternately arranged and connected along the width direction of the negative electrode film layer. The expansion degree of the negative pole piece in the plane direction is reduced, the surface and the edge of the negative pole piece are free of wrinkles, the polarization defect caused by surface expansion of the negative pole piece is overcome, and the cycle performance of the secondary battery is improved.
Description
Technical Field
The application relates to the technical field of secondary batteries, in particular to a negative pole piece, a secondary battery, a battery module, a battery pack and an electric device.
Background
In recent years, with the wider application range of secondary batteries, secondary batteries are widely used in energy storage power systems such as hydraulic power, thermal power, wind power, and solar power stations, and in various fields such as electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, and aerospace. As the development of secondary batteries has been greatly advanced, higher requirements are also placed on energy density, cycle performance, safety performance, and the like.
The silicon-carbon negative pole piece is an important direction for developing a high-energy-density secondary battery in the future, however, the expansion problem of the silicon-carbon negative pole piece in the plane direction is increasingly prominent, the problems that the surface of the negative pole piece is irregularly wrinkled and separated from lithium, the root of a tab is wrinkled and the like are caused, and the cycle life of the secondary battery is shortened.
SUMMERY OF THE UTILITY MODEL
The present invention has been made in view of the above problems, and an object of the present invention is to provide a negative electrode sheet, a secondary battery, a battery module, a battery pack, and an electric device, which solve the problem of wrinkling of the negative electrode sheet in the planar direction, the problem of polarization caused by wrinkling of the edge of the negative electrode sheet, and the problem of degradation of cycle performance of the secondary battery caused by the wrinkling.
In order to achieve the above object, a first aspect of the present application provides a negative electrode tab, including a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector; the negative electrode film layer comprises carbon material sections and silicon/carbon composite material sections, and the carbon material sections and the silicon/carbon composite material sections are alternately arranged and connected along the width direction of the negative electrode film layer.
Therefore, the expansion degree of the negative pole piece in the plane direction is reduced through the structure that the carbon material sections and the silicon/carbon composite material sections are alternately arranged and connected along the width direction of the negative pole film layer, so that the surface and the edge of the negative pole piece are smooth and have no wrinkles, the polarization defect caused by the surface expansion of the negative pole piece is overcome, and the cycle capacity retention rate and the cycle life of the secondary battery are improved.
In any embodiment, the negative electrode film layer has carbon material segments at both ends in the width direction. The arrangement is favorable for further relieving the expansion degree of the edge of the negative pole piece, so that the edge of the pole piece has no wrinkles, the polarization defect caused by the surface expansion of the negative pole piece is further overcome, and the cycle performance of the secondary battery is further improved.
In any embodiment, the number of carbon material segments is greater than the number of silicon/carbon composite segments in each anode film layer.
In any embodiment, the number of carbon material segments is 1 more than the number of silicon/carbon composite segments in each anode film layer.
The arrangement is beneficial to arranging more carbon material sections on two sides of the silicon/carbon composite material section so as to further reduce the expansion degree of the negative pole piece in the plane direction, so that the surface and the edge of the negative pole piece are free from wrinkles, the polarization caused by the surface expansion of the negative pole piece is further reduced, and the cycle performance of the secondary battery is further improved.
In any embodiment, the number of carbon material segments is selected from an integer in the range of 2 to 6 and the number of silicon/carbon composite segments is selected from an integer in the range of 1 to 5 per anode film layer. Compared with a certain number of silicon/carbon composite material sections, the sufficient number of carbon material sections can reduce the expansion degree of the negative pole piece in the plane direction, keep the surface and the edge of the negative pole piece smooth, reduce the polarization caused by the surface expansion of the negative pole piece and improve the cycle performance of the secondary battery.
In any embodiment, the ratio of the width of the carbon material section to the width of the silicon/carbon composite section is 5:1 to 1:1. Compared with the silicon/carbon composite material section, the carbon material section with enough area is arranged, so that the expansion degree of the negative pole piece in the plane direction is further reduced, the flatness of the surface and the edge of the negative pole piece is improved, the polarization caused by the surface expansion of the negative pole piece is further reduced, and the cycle performance of the secondary battery is further improved.
The second aspect of the present application provides a secondary battery, including the negative pole piece and the utmost point ear of the first aspect of this application, utmost point ear setting is at the width direction's of negative pole piece tip. .
A third aspect of the present application provides a battery module including the secondary battery of the second aspect of the present application.
A fourth aspect of the present application provides a battery pack including the battery module of the third aspect of the present application.
A fifth aspect of the present application provides an electric device including at least one selected from the secondary battery of the second aspect of the present application, the battery module of the third aspect of the present application, or the battery pack of the fourth aspect of the present application.
Drawings
Fig. 1 is a schematic view of a secondary battery according to an embodiment of the present application.
Fig. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in fig. 1.
Fig. 3 is a schematic view of a battery module according to an embodiment of the present application.
Fig. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
Fig. 5 is an exploded view of the battery pack according to the embodiment of the present application shown in fig. 4.
Fig. 6 is a schematic diagram of an electric device in which a secondary battery according to an embodiment of the present application is used as a power source.
Fig. 7 is a schematic structural diagram of a negative electrode tab in an embodiment of the present application.
Fig. 8 is an ac impedance spectrum of the secondary battery in the example of the present application.
Fig. 9 is a test chart of the retention ratio of the cycle capacity of the secondary battery of the example of the present application and the comparative battery.
Description of reference numerals:
1, a battery pack; 2, putting the box body on the box body; 3, discharging the box body; 4 a battery module; 5 a secondary battery; 51 a housing; 52 an electrode assembly; 53 a cap assembly.
Detailed Description
Hereinafter, embodiments of the negative electrode sheet, the secondary battery, the battery module, the battery pack, and the electric device according to the present invention are specifically disclosed in detail with reference to the drawings as appropriate. But a detailed description thereof will be omitted. For example, detailed descriptions of already known matters and repetitive descriptions of actually the same configurations may be omitted. This is to avoid unnecessarily obscuring the following description, and to facilitate understanding by those skilled in the art. The drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.
The "ranges" disclosed herein are defined in terms of lower limits and upper limits, with a given range being defined by a selection of one lower limit and one upper limit that define the boundaries of the particular range. Ranges defined in this manner may or may not include endpoints and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Further, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise stated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 to 5" have been listed herein, and "0 to 5" is only a shorthand representation of the combination of these numbers. In addition, when a parameter is an integer of 2 or more, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, or the like.
All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, if not specifically stated.
All technical and optional features of the present application may be combined with each other to form new solutions, if not otherwise specified.
All steps of the present application may be performed sequentially or randomly, preferably sequentially, if not specifically stated. For example, a method comprising steps (a) and (b) means that the method may comprise steps (a) and (b) performed sequentially, and may also comprise steps (b) and (a) performed sequentially. For example, reference to a process further comprising step (c) means that step (c) may be added to the process in any order, for example, the process may comprise steps (a), (b) and (c), may also comprise steps (a), (c) and (b), may also comprise steps (c), (a) and (b), etc.
The terms "comprises" and "comprising" as used herein mean either open or closed unless otherwise specified. For example, "comprising" and "comprises" may mean that other components not listed may also be included or included, or that only listed components may be included or included.
In this application, the term "or" is inclusive, if not otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or not present); a is false (or not present) and B is true (or present); or both a and B are true (or present).
[ Secondary Battery ]
A secondary battery is also called a rechargeable battery or a secondary battery, and refers to a battery that can be continuously used by activating an active material by means of charging after the battery is discharged.
In general, a secondary battery includes a positive electrode tab, a negative electrode tab, a separator, and an electrolyte. During the charging and discharging process of the battery, active ions (such as lithium ions) are inserted and extracted back and forth between the positive pole piece and the negative pole piece. The isolating membrane is arranged between the positive pole piece and the negative pole piece, mainly plays a role in preventing the short circuit of the positive pole and the negative pole, and can enable active ions to pass through. The electrolyte is arranged between the positive pole piece and the negative pole piece and mainly plays a role in conducting active ions.
Negative pole piece
One embodiment of the present application provides a negative electrode tab, including a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector; the negative electrode film layer comprises carbon material sections and silicon/carbon composite material sections, and the carbon material sections and the silicon/carbon composite material sections are alternately arranged and connected along the width direction of the negative electrode film layer. As an example, the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two surfaces opposite to the negative electrode current collector.
Although the mechanism is not clear, the applicant has surprisingly found that: this application sets up and meets structure along the width direction of negative pole rete in turn through carbon material district section and silicon/carbon combined material district section, utilizes the carbon material district section effectively to buffer the negative pole piece that the silicon material arouses along the bulging force of plane direction to reduce the inflation degree of negative pole piece in the plane direction, made the surface and the edge of negative pole piece level, no fold, overcome the polarization defect that negative pole piece surface inflation arouses, improved secondary battery's cycle capacity retention rate and cycle life.
In some embodiments, the two ends of the negative electrode film layer in the width direction are carbon material segments. The arrangement is favorable for further relieving the expansion of the edge of the negative pole piece, so that the edge of the pole piece has no wrinkles, the polarization defect caused by the surface expansion of the negative pole piece is further overcome, and the cycle performance of the secondary battery is further improved.
In some embodiments, the number of carbon material segments is greater than the number of silicon/carbon composite segments in each anode film layer.
In some embodiments, the number of carbon material segments is 1 more than the number of silicon/carbon composite segments in each anode film layer.
The carbon material sections with a large number are arranged on the two sides of the silicon/carbon composite material section, so that the expansion degree of the negative pole piece in the plane direction is further reduced, the surface and the edge of the negative pole piece are free from wrinkles, the polarization caused by the surface expansion of the negative pole piece is further reduced, and the cycle performance of the secondary battery is further improved.
In some embodiments, the number of carbon material segments is selected from an integer in the range of 2 to 6 and the number of silicon/carbon composite segments is selected from an integer in the range of 1 to 5 per anode film layer. Compared with a certain number of silicon/carbon composite material sections, the sufficient number of carbon material sections can reduce the expansion degree of the negative pole piece in the plane direction, keep the surface and the edge of the negative pole piece smooth, reduce the polarization caused by the surface expansion of the negative pole piece and improve the cycle performance of the secondary battery.
In some embodiments, the ratio of the width of the carbon material section to the width of the silicon/carbon composite section is 5:1 to 1:1. Compared with the silicon/carbon composite material section, the carbon material section with enough area is arranged, so that the expansion degree of the negative pole piece in the plane direction is further reduced, the flatness of the surface and the edge of the negative pole piece is further improved, the polarization caused by the surface expansion of the negative pole piece is further reduced, and the cycle performance of the secondary battery is further improved.
In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a base material of a polymer material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
In some embodiments, the carbon material is a negative active material known to those skilled in the art. Including but not limited to one or a mixture of several of the following: artificial graphite, natural graphite, soft carbon and hard carbon.
In some embodiments, the silicon/carbon composite is a negative active material known to those skilled in the art. The composite material comprises but is not limited to a composite material formed by mixing a silicon material and a carbon material, wherein the silicon material can be selected from at least one of simple substance silicon, silicon oxygen compound and silicon alloy, and the carbon material can be selected from at least one of artificial graphite, natural graphite, soft carbon and hard carbon; for example, a silica/carbon composite is a composite material formed by mixing silica and a carbon material, and a method for preparing the same is well known to those skilled in the art.
In some embodiments, the silicon/carbon composite (e.g., a silica/carbon composite) has a silicon content of 0% to 50% by mass.
In some embodiments, the anode film layer further optionally includes a binder. As an example, the binder may be selected from at least one of Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).
In some embodiments, the negative electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
In some embodiments, the negative electrode film layer may also optionally include other adjuvants, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.
In some embodiments, the negative electrode sheet can be prepared by: dispersing a carbon material, a conductive agent, a binder, and any other components in a solvent (e.g., deionized water) to form a first negative electrode slurry; dispersing the silicon/carbon composite material, the conductive agent, the binder and any other components in a solvent (such as deionized water) to form a second negative electrode slurry; and alternately and mutually coating the first negative electrode slurry and the second negative electrode slurry along the width direction of the negative electrode current collector, and drying, cold pressing and other procedures to obtain the negative electrode plate.
[ Positive electrode sheet ]
The positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.
As an example, the positive electrode current collector has two surfaces opposite in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two surfaces opposite to the positive electrode current collector.
In some embodiments, the positive electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a base material of a polymer material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
In some embodiments, the positive active material may employ a positive active material for a battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material of a battery may be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of the lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) 2 ) Lithium nickel oxide (e.g., liNiO) 2 ) Lithium manganese oxide (e.g., liMnO) 2 、LiMn 2 O 4 ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) 1/3 Co 1/3 Mn 1/3 O 2 (may also be abbreviated as NCM) 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (may also be abbreviated as NCM) 523 )、 LiNi 0.5 Co 0.25 Mn 0.25 O 2 (may also be abbreviated as NCM) 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (may also be abbreviated as NCM) 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (may also be abbreviated as NCM) 811 ) Lithium nickel cobalt aluminum oxides (e.g., liNi) 0.85 Co 0.15 Al 0.05 O 2 ) And modified compounds thereof, and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO) 4 (also referred to as LFP for short)), a composite material of lithium iron phosphate and carbon, and lithium manganese phosphate (e.g., liMnPO) 4 ) At least one of a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluoroacrylate resin.
In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and coating the positive electrode slurry on a positive electrode current collector, and drying, cold pressing and the like to obtain the positive electrode piece.
[ electrolyte ]
The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The kind of the electrolyte is not particularly limited and may be selected as desired. For example, the electrolyte may be liquid, gel, or all solid.
In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.
In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium dioxaoxalato borate, lithium difluorodioxaoxalato phosphate, and lithium tetrafluorooxalato phosphate.
In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, propyl methyl carbonate, propyl ethyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.
In some embodiments, the electrolyte further optionally includes an additive. By way of example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives capable of improving certain properties of the battery, such as additives that improve the overcharge properties of the battery, additives that improve the high-or low-temperature properties of the battery, and the like.
[ isolation film ]
In some embodiments, a separator is further included in the secondary battery. The type of the separator is not particularly limited, and any known separator having a porous structure and good chemical and mechanical stability may be used.
In some embodiments, the material of the isolation film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.
In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.
In some embodiments, the secondary battery may include an exterior package. The exterior package may be used to enclose the electrode assembly and electrolyte.
In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The outer package of the secondary battery may also be a pouch, such as a pouch-type pouch. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
The shape of the secondary battery is not particularly limited, and may be a cylindrical shape, a square shape, or any other arbitrary shape. For example, fig. 1 is a secondary battery 5 of a square structure as one example.
In some embodiments, referring to fig. 2, the overwrap may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose to form an accommodating cavity. The housing 51 has an opening communicating with the accommodating chamber, and a cover plate 53 can be provided to cover the opening to close the accommodating chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is enclosed within the receiving cavity. The electrolyte is impregnated into the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 may be one or more, and those skilled in the art can select them according to the actual needs.
In some embodiments, the secondary batteries may be assembled into a battery module, and the number of the secondary batteries included in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
Fig. 3 is a battery module 4 as an example. Referring to fig. 3, in the battery module 4, a plurality of secondary batteries 5 may be arranged in series along the longitudinal direction of the battery module 4. Of course, the arrangement may be in any other manner. The plurality of secondary batteries 5 may be further fixed by a fastener.
Alternatively, the battery module 4 may further include a case having an accommodation space in which the plurality of secondary batteries 5 are accommodated.
In some embodiments, the battery modules may be assembled into a battery pack, and the number of the battery modules contained in the battery pack may be one or more, and the specific number may be selected by one skilled in the art according to the application and the capacity of the battery pack.
Fig. 4 and 5 are a battery pack 1 as an example. Referring to fig. 4 and 5, a battery pack 1 may include a battery case and a plurality of battery modules 4 disposed in the battery case. The battery box comprises an upper box body 2 and a lower box body 3, wherein the upper box body 2 can be covered on the lower box body 3, and an enclosed space for accommodating the battery module 4 is formed. A plurality of battery modules 4 may be arranged in any manner in the battery box.
In addition, this application still provides an electric installation, and electric installation includes at least one in secondary battery, battery module or the battery package that this application provided. The secondary battery, the battery module, or the battery pack may be used as a power source of the electric device, and may also be used as an energy storage unit of the electric device. The powered device may include a mobile device (e.g., a mobile phone, a laptop computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, and a satellite, an energy storage system, etc., but is not limited thereto.
As the electricity-using device, a secondary battery, a battery module, or a battery pack may be selected according to its use requirement.
Fig. 6 is an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle or a plug-in hybrid electric vehicle and the like. In order to meet the demand of the electric device for high power and high energy density of the secondary battery, a battery pack or a battery module may be used.
[ examples ]
Hereinafter, examples of the present application will be described. The following description of the embodiments is merely exemplary in nature and is in no way intended to limit the present disclosure. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
Examples
1. Preparing a positive pole piece: dissolving a positive electrode active material lithium iron phosphate, a binder polyvinylidene fluoride (PVDF) and a conductive agent acetylene black in a solvent N-methyl pyrrolidone (NMP) according to a mass ratio of 97.8; and uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil, and then drying, cold pressing and slitting to obtain the positive electrode piece.
2. Preparing a negative pole piece: dissolving a negative electrode active material graphite material, a conductive agent acetylene black, a binder Styrene Butadiene Rubber (SBR), and a thickener sodium carboxymethyl cellulose (CMC-Na) in deionized water according to a mass ratio of 96.5; dissolving a negative electrode active material, namely a silicon monoxide/carbon composite material, a conductive agent, namely acetylene black, a binder, namely Styrene Butadiene Rubber (SBR), and a thickener, namely sodium carboxymethyl cellulose (CMC-Na), in deionized water according to a mass ratio of 95.3; and (3) sending the first negative electrode slurry and the second negative electrode slurry into different pipelines of a coating machine, coating the two slurries on two surfaces of a negative current collector copper foil alternately and in a connecting manner through a plurality of extrusion heads arranged on the coating machine according to design, and then drying, cold pressing and cutting to obtain a negative electrode pole piece. The structure of the negative electrode plate is shown in fig. 7, the negative electrode film layer of the negative electrode plate comprises carbon material sections (i, iii, v sections) and silicon/carbon composite material sections (ii, iv sections), and the carbon material sections and the silicon/carbon composite material sections are alternately arranged and connected along the width direction of the negative electrode film layer.
3. And (3) isolation film: a polypropylene film is used.
4. Preparing an electrolyte: ethylene Carbonate (EC), ethyl Methyl Carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1. In the electrolyte, the concentration of LiPF6 was 1mol/L.
5. Preparation of secondary battery: stacking and winding the positive pole piece, the isolating membrane and the negative pole piece in sequence to obtain an electrode assembly; and (3) putting the electrode assembly into an outer package, adding the prepared electrolyte, and carrying out processes of packaging, standing, formation, aging and the like to obtain the secondary battery.
Battery testing
(1) AC impedance testing
By utilizing an electrochemical workstation, a two-electrode system is adopted, a positive pole piece is taken as a working electrode, the edge and the middle part of a negative pole piece are respectively taken as counter electrodes, an alternating current perturbation signal is given to the system by adopting a constant potential method in a 100-percent SOC state, the signal frequency is changed by 0.01-10000 Hz, the alternating current response of the system is measured by the electrochemical workstation, and the impedance is obtained according to the proportion of voltage and current. The results are shown in FIG. 8.
As can be seen from fig. 8, the impedances measured at the edge and the middle of the negative electrode sheet are close to each other, which indicates that the negative electrode sheet of the present application does not have serious polarization difference, serious charge-discharge non-uniformity, or large expansion force variation to cause wrinkling of the negative electrode sheet.
(2) Test of retention rate of circulating capacity and surface observation of negative pole piece
The test method comprises the following steps: charging the secondary battery from 2.8V to 4.2V and then discharging to 2.8V at 25 ℃ using 1C charging and discharging current as a primary cycle, performing charging and discharging cycles using a 0% -100% dod interval for a total of 720 cycles; wherein, the charge and discharge are resumed once every time the integral multiple of 50 times, the charge and discharge current of 0.2C is adopted, the charge and discharge current is changed from 2.8V to 4.2V, then the discharge current is changed to 2.8V, and the DOD interval is changed by 0% -100%; the cycle capacity retention rate of the secondary battery was measured after each cycle.
The negative electrode sheet of the comparative cell was prepared by coating with the second negative electrode slurry alone, and the rest was the same as in the example.
The cycle capacity retention ratio was measured in the same manner as described above for the secondary battery of example and the comparative battery. The results are shown in FIG. 9.
After the cycle was completed, the secondary battery of the example was disassembled, and the negative electrode sheet was taken out to take a photograph.
As can be seen from fig. 9, the capacity of the comparative battery using the conventional negative electrode tab rapidly decays with the increase of the cycle number, and the capacity retention rate has decayed to 75% when the cycle number is less than 100 times; compared with the prior art, the capacity of the secondary battery slowly decays along with the increase of the cycle number, and the capacity retention rate is still more than 80% after 720 cycles, which shows that the cycle capacity retention rate of the secondary battery is higher.
The negative pole piece of the embodiment is observed after the circulation is finished, so that the surface of the negative pole piece is not wrinkled, and the water jump cannot occur in the cycle life of the secondary battery.
The present application is not limited to the above embodiments. The above embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exhibiting the same operation and effect within the technical scope of the present application are all included in the technical scope of the present application. In addition, various modifications that can be conceived by those skilled in the art are applied to the embodiments and other embodiments are also included in the scope of the present application, in which some of the constituent elements in the embodiments are combined and constructed, without departing from the scope of the present application.
Claims (10)
1. The negative pole piece is characterized by comprising a negative pole current collector and a negative pole film layer arranged on at least one surface of the negative pole current collector; the negative electrode film layer comprises carbon material sections and silicon/carbon composite material sections, and the carbon material sections and the silicon/carbon composite material sections are alternately arranged and connected along the width direction of the negative electrode film layer.
2. The negative electrode sheet according to claim 1, wherein the negative electrode film layer has carbon material segments at both ends in the width direction.
3. The negative electrode tab of claim 1, wherein the number of carbon material segments is greater than the number of silicon/carbon composite segments in each negative electrode film layer.
4. The negative electrode tab of claim 1, wherein the number of carbon material segments in each negative electrode film layer is 1 more than the number of silicon/carbon composite segments.
5. The negative electrode tab of claim 1, wherein the number of carbon material segments in each negative electrode film layer is selected from an integer in the range of 2 to 6, and the number of silicon/carbon composite segments is selected from an integer in the range of 1 to 5.
6. The negative electrode sheet of any one of claims 1 to 5, wherein the ratio of the width of the carbon material section to the width of the silicon/carbon composite section is 5:1-1:1.
7. A secondary battery comprising the negative electrode tab of any one of claims 1 to 6, and a tab provided at an end portion in a width direction of the negative electrode tab.
8. A battery module characterized by comprising the secondary battery according to claim 7.
9. A battery pack comprising the battery module according to claim 8.
10. An electric device comprising at least one selected from the group consisting of the secondary battery according to claim 7, the battery module according to claim 8, and the battery pack according to claim 9.
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| CN202220272014.9U CN217768423U (en) | 2022-02-10 | 2022-02-10 | Negative electrode plate, secondary battery, battery module, battery pack and electric device |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115832202A (en) * | 2022-12-21 | 2023-03-21 | 楚能新能源股份有限公司 | Negative pole piece, lithium ion battery and preparation method thereof |
| CN116344739A (en) * | 2023-05-29 | 2023-06-27 | 江苏正力新能电池技术有限公司 | Silicon-based negative electrode plate and application thereof |
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2022
- 2022-02-10 CN CN202220272014.9U patent/CN217768423U/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115832202A (en) * | 2022-12-21 | 2023-03-21 | 楚能新能源股份有限公司 | Negative pole piece, lithium ion battery and preparation method thereof |
| CN115832202B (en) * | 2022-12-21 | 2023-09-29 | 楚能新能源股份有限公司 | Negative electrode plate, lithium ion battery and preparation method of lithium ion battery |
| CN116344739A (en) * | 2023-05-29 | 2023-06-27 | 江苏正力新能电池技术有限公司 | Silicon-based negative electrode plate and application thereof |
| CN116344739B (en) * | 2023-05-29 | 2023-08-11 | 江苏正力新能电池技术有限公司 | Silicon-based negative electrode plate and application thereof |
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